慢性疼痛是多原因引起的高发顽固性病症，且缺乏特异性治疗措施。脊髓神经元可塑性改变被认为是慢性痛发生的关键环节，该改变很大程度上依赖于基因调控引起的膜上受体和离子通道变化，但慢性疼痛基因调控机制仍不清楚。cirRNA丰富表达于中枢神经系统，是基因表达调控新方式。预试验发现：慢性痛下，小鼠脊髓cirR-5252增加显著，下调cirR-5252能减轻疼痛；泛素连接酶Ubr5启动子有1个cirR-5252结合位点，下调cirR-5252能抑制Ubr5表达；Ubr5降低则能逆转钾离子通道Kcnd2表达；cirR-5252前体剪接点能被miRNA-1224结合，过表达miRNA-1224能降低cirR-5252表达但其前体无变化。因此，本项目拟用CFA模型小鼠，阐明受miRNA-1224靶向剪接调控的cirR-5252通过Ubr5泛素化修饰Kcnd2介导慢性炎性痛机制，以期为研发理想镇痛药提供新思路。

Chronic pain is a frequently-occurring and refractory disease, and lacks specific effective drugs in treatment. Central sensitization of spinal cord plays a critical role in the pathogenesis of chronic pain. The induction and maintenance of central sensitization are dependent on maladaptive alterations in the expression, distribution, and activity of receptors and ion channels on spinal neuronal membrane. Aberrant pain-related gene expression is one of most prominent contributors to these maladaptive processes. Therefore, the unraveling of the genetic basis and its regulatory mechanisms involved in central sensitization will improve our understanding of chronic pain and provide potential targets for developing novel therapeutic strategies. CircleRNA (cirRNA), a new regulatory mechanism of gene expression, attracts widespread attention on their potential role in complicated biological processes and human diseases. CirRNA is enriched in central nervous system, however, whether cirRNA could regulate chronic pain keeps unclear. In the preliminary experiment, the following critical results had been found. Firstly, cirRNA-5252 (cirR-5252) was significantly increased in spinal cord of Complete Freunds Adjuvant (CFA)-induced chronic inflammatory pain mice via high-throughput sequencing analysis. Knockdown of cirR-5252 with siRNA alleviated the pain sensitivity to the thermal or mechanical stimulus; on contrary, overexpression of cirR-5252 induced the production of the pain-like behavior. Secondly, cirR-5252 was predictively bound to the promoter of Ubr5, a ubiquitin ligase. Downregulation of cirR-5252 reversed the increased Ubr5 protein in spinal cord of CFA-induced pain mice. Additionally, knockdown of cirR-5252 with anti-RNA inhibited the pain behavior, suggesting Ubr5 is a possible positive regulatory target of cirR-5252. Thirdly, the decreased Kcnd2 protein, a voltage-gated potassium channel, was reversed by downregulation of Ubr5 in spinal cord of CFA-induced pain mice. Finally, miRNA-1224 was predicted to bind to the splicing point of cirR-5252 precursor. Overexpression of spinal miRNA-1224 inhibited the expression of spinal cirR-5252, and significantly alleviated pain induced by CFA. Therefore, the purpose of this study is to investigate whether cirR-5252 spliced by miRNA-1224 could modulate chronic inflammatory pain through ubiquitination-modified Kcnd2 by Ubr5 at the spinal cord level. This study will reveal a new functional regulatory mechanism underlying chronic pain process, which will provide a possible target for the development of analgesic drugs.